Modern biochemical methodology will be used for a systematic comparative study of the acetylcholine (ACh) system (ACh; choline acetyltransferase, ChAc; cholinesterases, ChE; ACh-receptor) in nonnervous tissue of placentae from various mammalian species. The study will include experiments on ACh synthesis, storage, release and turnover. The effect of drugs on those parameters will be measured and compared to nervous tissue. Fetal membranes and fluids will be included for analysis. ACh will be determined by gas chromatography, ChAc and ChE with radiometric methods. The project will involve the in vitro use of a bilaterally perfused single cotyledon from human placenta and of in situ perfused guinea pig placenta. Experiments will be performed to establish whether there is an ACh-receptor-like material in placenta which binds H3-muscarone, a labelling drug of high specificity and affinity which binds to muscarinic and nicotinic cholinergic receptors as defined in innervated tissue. The influence of changes in concentration of ACh on some metabolic functions in placenta will be examined, among them protein and phospholipid synthesis, and on permeability regulation as well as active transport of ions and amino acids.